Wild rocket (Diplotaxis tenuifolia) is a specialty leaf vegetable also known as rucola and arugula. Wild rocket is a quick growing crop grown for its leaves. Due to its pleasant taste it is often used as an ingredient in salads and other dishes.
In many production areas the production of wild rocket is being hindered by the infection of the plants by downy mildew (Hyaloperonospora parasitica, previously called Peronospora parasitica). Downy mildew is a polycyclic disease caused by different species of the oomycete Hyaloperonospora. The obligate parasite from the genus Hyaloperonospora is living on Brassica plants and related cruciferous crops. The losses are more severe at the seedling stage than on mature healthy plants. Young seedlings can die as a result of the infection. Cool and moist conditions are favorable for the disease development. The disease causes quantitative and qualitative losses of the crops. Although all (aerial) parts of the plant can be infected, the symptoms primarily appear on the leaves. Symptoms of the disease such as discolored lesions and necrotic spots with brown edges can destroy the quality of the leaves. Also the quantity of the harvest is reduced due to the downy mildew infection.
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